When You Turn Off A Light, Where Does The Light Go?

In space, light will go on, and on, and on… In a windowless room, where does the light go when we switch it off?

Originally posted on Forbes!

Light is a pretty simple beast. In lieu of any interference, it will go on, and on, and on, as we see it doing in the vast, often empty, realms of interstellar and intergalactic space.

Space is a rather unique case, because in between massive objects, light is traveling through something very close to a pure vacuum. This vacuum environment it's traveling through means that there’s very little chance for the light to run into any kind of interference - it's relatively easy for the light to travel enormous distances without anything changing its path or blocking its way.

So what are the options if there is something in the way? Well, light functionally has two options: reflection or absorption. Reflection we’re quite familiar with, as it’s the physics behind seeing yourself in a mirror. This can happen anytime light hits a surface which is smooth, to its perspective. (The smoothness required depends on the wavelength of the light - optical light needs a smoother surface to reflect cleanly off of than radio waves do, which are much longer in wavelength.)

The other option is absorption. This is the process which makes rocks warm in the sun. The rocks are absorbing sunlight over time, and over that time, the energy collected into the rock will warm the surface. Any light can be absorbed, not just the infrared (heat) portion of sunlight. A terrible mirror could absorb enough light that your reflection is only a faint ghost of an image. Unless you’ve got an old filament bulb left in your lamps, you won’t notice an appreciable warming to any of your possessions, because most light bulbs nowadays are designed very specifically not to produce much heat. We can’t see it, and it’s a waste of energy to produce heat which doesn’t help us see the room.

These one-light-year-tall pillars of cold hydrogen and dust, imaged by the Hubble Space Telescope, are located in the Carina Nebula. This image of dust pillars in the Carina Nebula is a composite of 2005 observations taken of the region in hydrogen light (light emitted by hydrogen atoms) along with 2010 observations taken in oxygen light (light emitted by oxygen atoms), both times with Hubble's Advanced Camera for Surveys. The immense Carina Nebula is an estimated 7,500 light-years away in the southern constellation Carina. NASA, ESA, and the Hubble Heritage Project (STScI/AURA); Acknowledgment: M. Livio (STScI) and N. Smith (University of California, Berkeley)

These one-light-year-tall pillars of cold hydrogen and dust, imaged by the Hubble Space Telescope, are located in the Carina Nebula. This image of dust pillars in the Carina Nebula is a composite of 2005 observations taken of the region in hydrogen light (light emitted by hydrogen atoms) along with 2010 observations taken in oxygen light (light emitted by oxygen atoms), both times with Hubble's Advanced Camera for Surveys. The immense Carina Nebula is an estimated 7,500 light-years away in the southern constellation Carina. NASA, ESA, and the Hubble Heritage Project (STScI/AURA); Acknowledgment: M. Livio (STScI) and N. Smith (University of California, Berkeley)

These two options, absorption and reflection, work in tandem with each other, and most materials will do a little of both. Even your standard bathroom mirror absorbs a little of the light that hits it (typically about 10%), and few naturally occurring materials on Earth are perfect light absorbers. Some ultra-black materials are getting very close, but the only truly perfectly absorbing objects around so far are black body objects; an object heated until it glows. (An old filament light bulb would count.)

So, when considering what happens to the light from your light bulb when you switch it off, let’s consider what’s happening when we have the light on. Light is being continually produced by the bulb, which is streaming outwards through the air, mostly unperturbed by having to go through air instead of a vacuum. It will then hit every surface which faces the bulb, and some fraction of it will reflect in the direction of your eyeballs, which will absorb the light, and tell you how bright the room is, along with some information about the objects within the room.

NGC 1999 is an example of a reflection nebula. Like fog around a street lamp, a reflection nebula shines only because the light from an embedded source illuminates its dust; the nebula does not emit any visible light of its own. NGC 1999 lies close to the famous Orion Nebula, about 1,500 light-years from Earth, in a region of our Milky Way galaxy where new stars are being formed actively.  Image Credit: NASA and The Hubble Heritage Team (STScI)

NGC 1999 is an example of a reflection nebula. Like fog around a street lamp, a reflection nebula shines only because the light from an embedded source illuminates its dust; the nebula does not emit any visible light of its own. NGC 1999 lies close to the famous Orion Nebula, about 1,500 light-years from Earth, in a region of our Milky Way galaxy where new stars are being formed actively.  Image Credit: NASA and The Hubble Heritage Team (STScI)

The difference between this situation and switching the light off is simply that you’re no longer replacing the absorbed photons of light with new ones. The last rays of light that the light bulb produced will behave exactly as the rest of the light did: either absorbing into or reflecting off of the various surfaces in your room. The reflected light will bounce until it’s absorbed, but considering how fast the photon can traverse the room, and how few bounces it takes to absorb light, this loss of light is functionally instantaneous.

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What Does The Sun Sound Like?

What sound does the Sun make, and would it be musical if we could hear it?
This montage of 366 images shows our Sun through the eyes of ESA’s Proba-2 satellite, as seen each day in 2016. The satellite’s SWAP camera works at extreme ultraviolet wavelengths to capture the hot turbulent atmosphere of the Sun, known as the solar corona. Each image was created from 30 separate images centred on 01:00 GMT each day, which were processed to enhance the features extending from the solar disc. Throughout 2016 the Sun’s 11 year activity cycle continued towards its minimum, a period when the number of sunspots, active regions, solar flares and eruptions diminish. Nonetheless, the most active region of last year can be seen in the 17 July image. The bright region close to the centre of the Sun produced eight of the 20 most powerful flares witnessed last year. Other prominent features are coronal holes – darker regions indicating lower levels of emission. However, coronal holes can produce streams of fast solar wind that can trigger geomagnetic storms on Earth. One of the largest holes observed last year can be seen towards the north of the Sun on 24 November, and was present for several solar rotations. Image credit: ESA/Royal Observatory of Belgium

This montage of 366 images shows our Sun through the eyes of ESA’s Proba-2 satellite, as seen each day in 2016. The satellite’s SWAP camera works at extreme ultraviolet wavelengths to capture the hot turbulent atmosphere of the Sun, known as the solar corona. Each image was created from 30 separate images centred on 01:00 GMT each day, which were processed to enhance the features extending from the solar disc. Throughout 2016 the Sun’s 11 year activity cycle continued towards its minimum, a period when the number of sunspots, active regions, solar flares and eruptions diminish. Nonetheless, the most active region of last year can be seen in the 17 July image. The bright region close to the centre of the Sun produced eight of the 20 most powerful flares witnessed last year. Other prominent features are coronal holes – darker regions indicating lower levels of emission. However, coronal holes can produce streams of fast solar wind that can trigger geomagnetic storms on Earth. One of the largest holes observed last year can be seen towards the north of the Sun on 24 November, and was present for several solar rotations. Image credit: ESA/Royal Observatory of Belgium

Originally posted on Forbes!

Sound is a tricky thing in space. Sound is a pressure wave, an oscillation in the density of air or water, which moves through the air or through water until it reaches something it can rattle. If that sound is reaching a human ear, and if the oscillation is within the range of frequencies we are sensitive to, it will be heard. Our Earth produces a number of these pressure waves, from the sound of a person next to you speaking, or the crash of a wave on a beach, or a sonic boom of an airplane above you. However, there are plenty of sounds produced which we are outside our range of hearing - with an instrument tuned to receive those pressure waves, we can prove their presence, but it would be impossible to play back and hear it without speeding up the recording.

In space, we have a major problem with recording sounds; there’s no atmosphere for sound waves to travel through, so any pressure waves an object may be producing will be instantly silenced without a medium to compress. However, if you’re clever about it, there are other ways of recording information which can be translated into a sound; the easiest one is vibrations. The ‘crunch’ of Philae, Rosetta’s lander on the comet 67P, hitting the surface of the comet made the rounds - but this noise is not, in fact, the result of a microphone on the landerThis noise is a translation of the vibrations of the feet of the lander at the moment when it hit the surface of the comet.

Rosetta’s lander Philae has been identified in OSIRIS narrow-angle camera images taken on 2 September 2016 from a distance of 2.7 km. The image scale is about 5 cm/pixel. Philae’s 1 m-wide body and two of its three legs can be seen extended from the body. The images also provide proof of Philae’s orientation. A Rosetta Navigation Camera image taken on 16 April 2015 is shown at top right for context, with the approximate location of Philae on the small lobe of Comet Churyumov-Gerasimenko marked. Main image and lander inset: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; context: ESA/Rosetta/NavCam, CC BY-SA IGO 3.0

Rosetta’s lander Philae has been identified in OSIRIS narrow-angle camera images taken on 2 September 2016 from a distance of 2.7 km. The image scale is about 5 cm/pixel. Philae’s 1 m-wide body and two of its three legs can be seen extended from the body. The images also provide proof of Philae’s orientation. A Rosetta Navigation Camera image taken on 16 April 2015 is shown at top right for context, with the approximate location of Philae on the small lobe of Comet Churyumov-Gerasimenko marked. Main image and lander inset: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; context: ESA/Rosetta/NavCam, CC BY-SA IGO 3.0

However, if you want to translate a data set into sound, you’re not limited to just dealing with vibrations. You can turn pretty much anything into a set of tones, if you’re creative enough. Sonification is a booming area of data manipulation -- it’s another face of the data visualization scene; instead of presenting the information visually, you can code it audibly, and listen to it over time. You simply have to decide what you want the pitch of the musical note to correspond to, what you want the timing between each note to correspond to, and what you want the volume to correspond to.

For data coming from a spacecraft which monitors the Sun, there is often a new image every hour and a half or so. In this case, the pacing between notes is easily given to the time between observations, which will form a regular cadence. However, extracting a volume and pitch out of the data will depend very much on exactly what part of the data you’re interested in reflecting.

For Rosetta’s “singing comet” sonification, there was a very low frequency oscillation in the magnetic field surrounding the comet, measured by Rosetta. The decision here was to use the frequency of that vibration in the magnetic field as the pitch, but sped up by a factor of 10,000, so that it could register in the human ear. The volume here is driven by how large the oscillations were, much as it would be for a sound wave on Earth.

Single frame enhanced NavCam image taken on 27 March 2016, when Rosetta was 329 km from the nucleus of Comet 67P/Churyumov-Gerasimenko. The scale is 28 m/pixel and the image measures 28.7 km across. Image credit: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0

Single frame enhanced NavCam image taken on 27 March 2016, when Rosetta was 329 km from the nucleus of Comet 67P/Churyumov-Gerasimenko. The scale is 28 m/pixel and the image measures 28.7 km across. Image credit: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0

For the Sun, not only do we have to speed up the oscillation, but we also have to choose which observed oscillation we want to convert into a sound. The most common choice that I found was to examine the roiling surface of the Sun, which resembles nothing more than a pot of water at high boil. You could imagine examining how high the bubbles rise above the surface, and how quickly they do so. If we convert this amplitude and rapidity into a volume and a tone, we can get a musical note out for every bubble that rises to the surface. This is only one of many possible optionsfor sonifying the Sun, but it seems to be one of the more common choices.

What do we hear? Here’s a few examples.

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Is There Any Way To Slow Down A Solar Sail?

I recently read an article about a project called Breakthrough Starshot. It’s been proposed to send a tiny craft to Alpha Centauri at 20% the speed of light and the craft(s) would arrive in 20 years or so. Let’s say that there’s been a successful launch and the tiny ship is on it’s way. Would Alpha Centauri have enough gravitational pull to capture an object moving that fast or would it be a one time fly by like New Horizons and Pluto?
This image shows the closest stellar system to the Sun, the bright double star Alpha Centauri AB and its distant and faint companion Proxima Centauri. In late 2016 ESO signed an agreement with the Breakthrough Initiatives to adapt the VLT instrumentation to conduct a search for planets in the Alpha Centauri system. Such planets could be the targets for an eventual launch of miniature space probes by the Breakthrough Starshot Initiative. Image Credit: ESO/B. Tafreshi (twanight.org)/Digitized Sky Survey 2 Acknowledgement: Davide De Martin/Mahdi Zamani

This image shows the closest stellar system to the Sun, the bright double star Alpha Centauri AB and its distant and faint companion Proxima Centauri. In late 2016 ESO signed an agreement with the Breakthrough Initiatives to adapt the VLT instrumentation to conduct a search for planets in the Alpha Centauri system. Such planets could be the targets for an eventual launch of miniature space probes by the Breakthrough Starshot Initiative. Image Credit: ESO/B. Tafreshi (twanight.org)/Digitized Sky Survey 2 Acknowledgement: Davide De Martin/Mahdi Zamani

Originally posted on Forbes!

You’ve got a pretty good handle on Breakthrough Starshot - their goal is indeed to ship off a tiny little craft, attached to a huge solar sail, and use high powered lasers to accelerate the craft to a speed much faster than what the power of the sun could do alone.

The spacecraft itself will have no thrusters on it - the whole point is to keep the spacecraft as light as possible so it’s easier to accelerate to relativistic speeds. The more massive your object, the more energy it takes in order to increase its speed, and getting any object up to fractions of the speed of light is difficult under any circumstances. The strategy is to make a very light, thin (but large) sail, so that a very powerful laser can bounce off of it, gradually pushing the sail along faster and faster. The actual science instruments would be relatively tiny, suspended in the very middle of the sail, weighing as little as possible, while still being able to do the science required. (We are a significant technological distance from being able to do accomplish any kind of interstellar solar sail.)

The complete lack of thrusters, plus the single direction we can push from, does mean that once the spacecraft gets up to 20% of the speed of light, it’s not slowing down again unless it crashes into something. The gravitational pull of Alpha Centauri is certainly present, but as that star is only a little bit larger than our own Sun, it doesn’t have the kind of extreme gravitational pull you’d need to slow the craft down as it goes past. Not without stopping it violently, through a collision, anyhow. At best, you’d swing past the star, get a few good images, and then sling your spacecraft right on through the solar system and out the other side - just like New Horizons did for its flyby of Pluto.

Plutonian landscapes in twilight, under a hazy sky. Credit: NASA/JHU APL/SwRI

Plutonian landscapes in twilight, under a hazy sky. Credit: NASA/JHU APL/SwRI

However, New Horizons had a bit more control over itself coming into its Pluto encounter than any solar sail craft would. New Horizons does have thrusters- which meant it could make adjustments to its flight en route to Pluto, and that it could course correct into a good path to encounter another object, out beyond Pluto.

Using only gravitational arguments, any solar sail spacecraft is doomed to speed up and then pretty much continue to cruise at that speed. However - it’s possible that with a very careful calculation of the spacecraft’s trajectory, you might be able to slow down the spacecraft with another method. Stars very clearly have strong, non-gravitational influences over the region surrounding them, once you get up close. It’s not just our star that has a solar wind that could be used to propel a solar sail - every star has a solar wind.

This image is of a four-quadrant solar sail system, measuring 66 feet on each side that was tested in 2005 in the world's largest vacuum chamber at NASA's Glenn Research Center at Plum Brook Station in Sandusky, Ohio. Image Credit: NASA

This image is of a four-quadrant solar sail system, measuring 66 feet on each side that was tested in 2005 in the world's largest vacuum chamber at NASA's Glenn Research Center at Plum Brook Station in Sandusky, Ohio. Image Credit: NASA

A recent paper worked out how the solar wind of the star you’re heading towards could help slow down a solar sail, perhaps enough to send it into orbit around its destination star. There are a bunch of limitations to this approach - the biggest one being that solar sail has to be able to endure quite a rapid deceleration - if the sail shreds, you’re not stopping the craft. The sail also has to be relatively gigantic - their calculations rely on something about 315 meters to a side, which is much larger than anything we’ve currently built. (The most massive one currently underway is 50 meters to a side.)

The orbit also has to be pretty precisely known - according to this paper, if you come too close to the star, you destroy the solar sail and crash into the star. However, you’d still have to sail into the solar system veryvery, close to the star for the pressure from the star to slow down your spacecraft. It’s an extremely narrow range of allowable arrival positions, which the authors measure in solar radii. On an astronomical scale, this is tiny. You’re aiming to sail in to a solar system, so close to the star that you'd be about 20 times close to the Sun than Mercury, if you were arriving in our solar system. If your solar sail were a comet, this would put you in sungrazer territory.

The difficulty of managing this needle-threading exercise aside, there are still a number of technological problems - the calculation assumes that the solar sail is made of graphene, for its lightweight nature and relative strength. Graphene is not very reflective, though, which means that we'd have to get really good at coating extraordinarily thin layers of graphene with something reflective without making it brittle and prone to tearing. In principle, it's physically possible. It's just technologically improbable, for the moment.

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Would You Float At The Core Of The Earth?

Thought experiment...if you built a bedroom sized room at the center of the Earth, and you are in that room, which way is down? Please explain to me why if you are surrounded by the same amount of mass in every direction, how does that NOT EQUAL NET ZERO? In other words, would that not be the exact same thing as weightlessness? So what would an illustration of the curvature of Space look like at the center of a massive body? Wouldn’t there be a vortex of some sort? It’s kind of important to me to understand where I’m going wrong?
A 'Blue Marble' image of the Earth taken from the VIIRS instrument aboard NASA's most recently launched Earth-observing satellite - Suomi NPP. This composite image uses a number of swaths of the Earth's surface taken on January 4, 2012. The NPP satellite was renamed 'Suomi NPP' on January 24, 2012 to honor the late Verner E. Suomi of the University of Wisconsin. Image Credit: NASA/NOAA/GSFC/Suomi NPP/VIIRS/Norman Kuring

A 'Blue Marble' image of the Earth taken from the VIIRS instrument aboard NASA's most recently launched Earth-observing satellite - Suomi NPP. This composite image uses a number of swaths of the Earth's surface taken on January 4, 2012. The NPP satellite was renamed 'Suomi NPP' on January 24, 2012 to honor the late Verner E. Suomi of the University of Wisconsin. Image Credit: NASA/NOAA/GSFC/Suomi NPP/VIIRS/Norman Kuring

Originally posted at Forbes!

You very nearly got there! Let’s run with your example of a small room at the center of the Earth, but for my sanity, I’m going to make your room a sphere instead of a square, because everything else involved in this example is going to be round, and it makes the example easier.

So; gravity pulls on any object with a force that’s related to the masses of the two objects involved, and inversely related to the distance between them. This tells us that the more massive the two objects, the greater the pull, and the greater the distance between them, the weaker the influence. For us, on the surface of the Earth, we can work out how strong gravity is. All you need is the mass of the Earth, the mass of a human, and the distance between the center of the Earth and the surface of the Earth.

The mass of the Earth in kilograms is 5.972 × 10^24. 10^24 is a septillion, which is a number so outrageously large that it might be more manageable to think about as a trillion trillion kilograms. (In SI units, which most physicists use, this is gives you the prefix yotta. 5972 yottagrams! It’s fun to say.)  The mass of a human, in comparison, is negligible. The radius of the Earth is 3,959 miles - 6,371 km. If you plug these numbers in, you pull out the gravitational acceleration at the surface of the Earth; 9.81 meters per second every second. This pulls you in towards the surface of the planet.

Photographed from a shuttle training aircraft, space shuttle Endeavour and its six-member STS-134 crew head toward Earth orbit and rendezvous with the International Space Station. Liftoff was at 8:56 a.m. (EDT) on May 16, 2011, from Launch Pad 39A at NASA's Kennedy Space Center. Onboard are NASA astronauts Mark Kelly, commander; Greg H. Johnson, pilot; Michael Fincke, Andrew Feustel, Greg Chamitoff and European Space Agency astronaut Roberto Vittori, all mission specialists. STS-134 will deliver the Alpha Magnetic Spectrometer-2 (AMS), Express Logistics Carrier-3, a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the International Space Station. STS-134 is the final spaceflight for Endeavour. Image credit: NASA

Photographed from a shuttle training aircraft, space shuttle Endeavour and its six-member STS-134 crew head toward Earth orbit and rendezvous with the International Space Station. Liftoff was at 8:56 a.m. (EDT) on May 16, 2011, from Launch Pad 39A at NASA's Kennedy Space Center. Onboard are NASA astronauts Mark Kelly, commander; Greg H. Johnson, pilot; Michael Fincke, Andrew Feustel, Greg Chamitoff and European Space Agency astronaut Roberto Vittori, all mission specialists. STS-134 will deliver the Alpha Magnetic Spectrometer-2 (AMS), Express Logistics Carrier-3, a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the International Space Station. STS-134 is the final spaceflight for Endeavour. Image credit: NASA

Now, we’ve done something sneaky here, which is to assume that we can place the entire mass of the Earth at the very center of the Earth, and consider ourselves simultaneously at the surface, and six thousand kilometers away from the Earth’s mass. We can do this because the Earth is a sphere, and that means that there's an awful lot of symmetry to work with. You can also do the math very carefully, considering the pull of the Earth’s mass to the left of you, which will pull you slightly to the left, and the pull of the Earth’s mass to the right of you, which pulls you equally strongly to the right. There’s no net force going sideways, because you’re standing on a symmetric planet, and all the left and right directions will cancel out. All that’s left is the 'downward' direction.

Again, if you do it carefully, you have to consider the gravitational pull from the ground directly beneath your feet (which is quite close) and the ground on the opposite side of the planet, which is 7918 miles away. There’s the same amount of planet closer to you and farther from you (relative to the center of our planet), so on average, the force is the same as if it came from a point at the center. Mathematically, our trick of assuming that the entire mass of the planet is contained at the core of the Earth is identical to doing it all very carefully, and it is much easier to do.

ESA’s Swarm satellites have led the discovery of a jet stream in the liquid iron part of Earth’s core 3000 km beneath the surface. In addition, Swarm satellite data show that this jet stream is speeding up. Launched in 2013, the Swarm trio is dedicated to identifying and measuring precisely the different magnetic signals that make up Earth’s magnetic field. Image credit: ESA CC BY-SA 3.0 IGO

ESA’s Swarm satellites have led the discovery of a jet stream in the liquid iron part of Earth’s core 3000 km beneath the surface. In addition, Swarm satellite data show that this jet stream is speeding up. Launched in 2013, the Swarm trio is dedicated to identifying and measuring precisely the different magnetic signals that make up Earth’s magnetic field. Image credit: ESA CC BY-SA 3.0 IGO

What does this mean for your spherical room at the core of the planet? Well, this principle of canceling out forces if they’re pulling on you in different directions still holds, and so you’re absolutely on the money to say that you should be weightless in there. You absolutely could float at the center of the planet; the entire mass of one half of the planet pulling you to the left would cancel the remaining mass of the planet pulling you to the right. And the same is true of being pulled upwards/downwards, or any direction that you care to slice the planet in half. There would be no 'down'.

What does a depiction of space time look like in the middle of the planet? Let’s remember that our depictions of space time usually depict divots surrounding massive objects, where gravity pulls you “down” into the gravitational well. With no gravitational force, and no 'down', your room in the core of the Earth would have a space-time curve that was very flat. No bending, no vortex. If there’s no net gravitational force, there can be no slant or directionality to space-time.

It’s flat because you’re at the very very bottom of the gravitational well. To leave your room at the center of the Earth, you’d have to climb your way all the way back up to the surface of the Earth, and as soon as you left, there would be a net force, pulling you back down. As you climb out, more and more of the Earth is left below you, and the downward dragging force you would feel would increase almost continuously until you reached the surface. The surface is a much more hospitable place, in any case; it’s got all my favorite things on it.

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How Long Until The Moon Slows The Earth To A 25 Hour Day?

At this rate of the Moon’s gravitational force slowing down Earth’s rotation, how long will it take to increase an hour to our day?
NASA's Lunar Reconnaissance Orbiter (LRO) recently captured a unique view of Earth from the spacecraft's vantage point in orbit around the moon. Image Credit: NASA/Goddard/Arizona State University

NASA's Lunar Reconnaissance Orbiter (LRO) recently captured a unique view of Earth from the spacecraft's vantage point in orbit around the moon. Image Credit: NASA/Goddard/Arizona State University

Originally posted on Forbes!

The Earth’s rotation is indeed being slowed down by the presence of the Moon - every year, the Moon gains a little energy from the Earth, and drifts a little farther away from us. This drift is imperceptible to the human eye, but measurable, with the aid of undertakings like the Lunar Laser Ranging Experiment, which regularly bounces a laser off of a retroreflector that Apollo astronauts placed there.

Both the drift of the Moon and the slowing of the rotation of the Earth are very very small effects- the slowing of the Earth’s rotation over the last 100 years is estimated to be about 1.4 milliseconds. That’s a slowing of 0.0014 seconds total, over 100 years. Another method of estimating the slowing of the Earth uses historical records of solar eclipses to figure out exactly how fast the Earth must have been rotating in the past, and comes up with an average slowing of 2.5 milliseconds each century. To extrapolate out into the future, I’m going to use the average of these two numbers, and guess that we’re dealing with a slowing of approximately 0.002 seconds every century.

As a point of reference, this rate of slowing means that it will take 25,000 years to add a half a second to the Earth’s day. A whole second will take 50,000 years.

The release of the first images from NOAA’s newest satellite, GOES-16, is the latest step in a new age of weather satellites. This composite color full-disk visible image is from 1:07 p.m. EDT on Jan. 15, 2017, and was created using several of the 16 spectral channels available on the GOES-16 Advanced Baseline Imager (ABI) instrument. The image shows North and South America and the surrounding oceans. GOES-16 observes Earth from an equatorial view approximately 22,300 miles high, creating full disk images like these, extending from the coast of West Africa, to Guam, and everything in between. Image Credit: NOAA/NASA

The release of the first images from NOAA’s newest satellite, GOES-16, is the latest step in a new age of weather satellites. This composite color full-disk visible image is from 1:07 p.m. EDT on Jan. 15, 2017, and was created using several of the 16 spectral channels available on the GOES-16 Advanced Baseline Imager (ABI) instrument. The image shows North and South America and the surrounding oceans. GOES-16 observes Earth from an equatorial view approximately 22,300 miles high, creating full disk images like these, extending from the coast of West Africa, to Guam, and everything in between. Image Credit: NOAA/NASA

To add an entire hour? Every hour contains 3,600 seconds - (60 minutes to an hour, and 60 seconds to a minute). And so, to wait long enough to gain 3,600 seconds, we’ll need to wait 50,000 years 3,600 times over - 180 million years.

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