Does The Expansion Of The Universe Affect The Constellations?

Considering the Universe’s expansion, has the distance of the stars like the Orion’s belt ones changed in a noticeable magnitude for our naked eyes along our lives? Or does the fact that they are in our galaxy maintain them at the same distance always?
Alnitak, Alnilam, and Mintaka, are the bright bluish stars from east to west (left to right) along the diagonal in this gorgeous cosmic vista. Otherwise known as the Belt of Orion, these three blue supergiant stars are hotter and much more massive than the Sun. They lie about 1,000 light-years away. Image credit: wikimedia user Astrowicht, CC BY-SA 3.0

Alnitak, Alnilam, and Mintaka, are the bright bluish stars from east to west (left to right) along the diagonal in this gorgeous cosmic vista. Otherwise known as the Belt of Orion, these three blue supergiant stars are hotter and much more massive than the Sun. They lie about 1,000 light-years away. Image credit: wikimedia user Astrowicht, CC BY-SA 3.0

Nothing in the universe is completely still, but our Universe behaves much more like your second option than the first one.

You’re absolutely right that things within the galaxy are not expanding along with the Universe at large, and this is because everything within the galaxy is gravitationally attached...

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Does The Earth's Magnetic Field Go Past The ISS?

Does the Earth’s magnetosphere encompass the ISS and does it offer the same protection as it does our atmosphere and planet?
A profile view of the magnetic field and density data. Image Credit: NASA's Scientific Visualization Studio, the Space Weather Research Center (SWRC), the Community-Coordinated Modeling Center (CCMC) and the Space Weather Modeling Framework (SWMF).

A profile view of the magnetic field and density data. Image Credit: NASA's Scientific Visualization Studio, the Space Weather Research Center (SWRC), the Community-Coordinated Modeling Center (CCMC) and the Space Weather Modeling Framework (SWMF).

The International Space Station, or ISS, orbits our planet once every ninety minutes at the lofty height of 400 kilometers (about 248 miles) above the surface of our planet. This altitude puts it pretty well above the vast majority of the atmosphere, but it doesn’t place it outside...

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Can The Mass Of An Object Ever Change?

What is the difference between “mass” and “rest mass” ? Does this mean that mass is not always the same?
Nuclear particle tracks in the ten-inch bubble chamber mounted inside a superconducting magnet at Argonne show what happened to two negative K mesons that entered the bubble chamber from Argonne's ZGS. c.1966 Image credit: US Department of Energy, public domain

Nuclear particle tracks in the ten-inch bubble chamber mounted inside a superconducting magnet at Argonne show what happened to two negative K mesons that entered the bubble chamber from Argonne's ZGS. c.1966 Image credit: US Department of Energy, public domain

This is a good question, and also a good reminder to be careful with one’s language when writing about physics!

Most of the time, if you’re reading an article, what we mean by mass and rest mass is exactly the same. Rest mass is a slightly more precise term...

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What Could Cause The Night Sky To Shimmer & Pulse With Light?

Hello, This morning my wife and I went to the local mountains to see the Perseids meteor shower as we often do. We arrived about 1am and both of us noticed the whole sky seemed to pulsate and shimmer with a faint light we had never seen before. We were wondering if this could be caused by the dust particles from the comet trail. It was even more noticeable with binoculars. Any suggestions would be appreciated. Thank you
Volume rendered image of a large eddy simulation of a non-premixed swirl flame. Image credit: Andreas Kempf, CC A-SA 3.0

Volume rendered image of a large eddy simulation of a non-premixed swirl flame. Image credit: Andreas Kempf, CC A-SA 3.0

There’s definitely some stuff happening to the atmosphere in the scenario you’re describing, but I doubt it’s likely to be caused by particles from the debris of comet’s tail.  The dust and pieces of grit are what you’re seeing as the meteor shower. The meteors you see during the Perseids will all...

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How Come I See Fewer Stars Than I Remember As A Child?

I’m past eighty years old. I remember as a child the stars looking like they were almost on top of us, so close and so bright and a billion of them to boot. Now they look so far away and almost faint. No it is not my eyesight. Have the stars moved away from us to that extent in just 80 years and if so how long before they are not seen at all.
The constellation Orion, imaged at left from dark skies, and at right from Orem, UT. Orem, UT is hardly a large city. This is intended to highlight the fact that light pollution is a problem everywhere, not just in cities with tens of millions of inhabitants. Image credit: Flickr user jpstanley, CC BY 2.0.

The constellation Orion, imaged at left from dark skies, and at right from Orem, UT. Orem, UT is hardly a large city. This is intended to highlight the fact that light pollution is a problem everywhere, not just in cities with tens of millions of inhabitants. Image credit: Flickr user jpstanley, CC BY 2.0.

Unfortunately, the stars haven’t moved, and I believe you that it’s not your eyesight either, because there’s another known and astronomically obnoxious thing that’s happened over the past decades. The amount of light pollution in the night skies has increased dramatically...

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Why Are We Limited To Only Seeing The Past?

We are moving from A to B. Yet everywhere we look, we are going backwards! I mean the direction we are moving along [trajectory] must [?] have something in front of earth-solar system-galaxy. Yet it is all the past. No future! Now could this be because we are at the event horizon [so to speak] the very edge of the beginning? However one ‘material’ that has moved faster-than-light is space. Light is still catching up. Why can’t we see even this?
Our solar journey through space is carrying us through a cluster of very low density interstellar clouds. Right now the Sun is inside of a cloud (Local cloud) that is so tenuous that the interstellar gas detected by IBEX is as sparse as a handful of air stretched over a column that is hundreds of light years long. These clouds are identified by their motions, indicated in this graphic with blue arrows. Credit: NASA/Goddard/Adler/U. Chicago/Wesleyan

Our solar journey through space is carrying us through a cluster of very low density interstellar clouds. Right now the Sun is inside of a cloud (Local cloud) that is so tenuous that the interstellar gas detected by IBEX is as sparse as a handful of air stretched over a column that is hundreds of light years long. These clouds are identified by their motions, indicated in this graphic with blue arrows. Credit: NASA/Goddard/Adler/U. Chicago/Wesleyan

There’s a couple things blurring together here, but the fundamental thing here is the distinction between the observable universe and the universe which exists, independent of our ability to observe it. You’ve got a good handle on the observable...

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How Far Could You Bounce A Laser Down A Hall Of Mirrors?

Hi! My question is if one has a ray of light to project at an unlimited amount of mirrors, how far could the ray of light be projected by transferring its reflection from each mirror?
Interior view of the Zürichsee-Schiffahrtsgesellschaft (ZSG) paddle steamship Stadt Zürich on Zürichsee (Lake Zürich) in Switzerland. Image credit: wikimedia user Roland zh, CC BY-SA 3.0

Interior view of the Zürichsee-Schiffahrtsgesellschaft (ZSG) paddle steamship Stadt Zürich on Zürichsee (Lake Zürich) in Switzerland. Image credit: wikimedia user Roland zh, CC BY-SA 3.0

All right, let’s tackle this one. To make this a little more straightforward, I’m going to assume you’re bouncing a laser beam down a hall of mirrors. In this case, your question is really how many bounces will the laser beam make before enough light is lost that no more bounces are...

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How Do Solar Sails Work?

I understand that a photon has no mass... so how can it be used to push a solar sail ? How can a “massless” thing transfer momentum?
A 20-meter solar sail and boom system, developed by ATK Space Systems of Goleta, Calif., is fully deployed during testing at NASA Glenn Research Center's Plum Brook facility in Sandusky, Ohio. Blue lights positioned beneath the system help illuminate the four triangular sail quadrants as they lie outstretched in Plum Brook's Space Power Facility -- the world's largest space environment simulation chamber. The sail material is supported by a series of coilable booms, which are extended via remote control from a central stowage container about the size of a suitcase, and is made of an aluminized, plastic-membrane material called CP-1. The material is produced under license by SRS Technologies of Huntsville, Ala. The deployment, part of a series of tests in April, is a critical milestone in the development of solar sail propulsion technology that could lead to more ambitious inner Solar System robotic exploration. Image credit: NASA

A 20-meter solar sail and boom system, developed by ATK Space Systems of Goleta, Calif., is fully deployed during testing at NASA Glenn Research Center's Plum Brook facility in Sandusky, Ohio. Blue lights positioned beneath the system help illuminate the four triangular sail quadrants as they lie outstretched in Plum Brook's Space Power Facility -- the world's largest space environment simulation chamber. The sail material is supported by a series of coilable booms, which are extended via remote control from a central stowage container about the size of a suitcase, and is made of an aluminized, plastic-membrane material called CP-1. The material is produced under license by SRS Technologies of Huntsville, Ala. The deployment, part of a series of tests in April, is a critical milestone in the development of solar sail propulsion technology that could lead to more ambitious inner Solar System robotic exploration. Image credit: NASA

This is not an easy thing to wrap one’s head around, and part of the reason it’s tricky is because light is a little special. Light manages to behave both like a particle and like a wave. In either case, you’re absolutely right that the particle of light...

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Will The Voyager Spacecraft Stop?

Hi, I’m wondering about the Voyager probes that are headed for interstellar space. Since they don’t have onboard propulsion, just gravity assisted forward motion and we now know that ‘empty’ space is not really empty, won’t the two crafts eventually lose momentum and become dead still in space essentially? Any thoughts on how long it would take?
Artist concept of NASA's Voyager spacecraft. Image credit: NASA/JPL-Caltech

Artist concept of NASA's Voyager spacecraft. Image credit: NASA/JPL-Caltech

The two Voyager spacecraft do actually have some propulsion on board - though you’re right that these thrusters are not where the majority of their forward motion is coming from. That outward speed comes from the combination of a high speed launch away from Earth, followed by a big gravitational slingshot past Jupiter...

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How Are Astronomical Distances Measured?

How is astronomical distance determined? Just cannot get my head around cepheid variables, parallax, etc. How is it possible to tell how far away something is when you cannot bounce a radar beam off the object and time its return?
RS Puppis rhythmically brightens and dims over a six-week cycle. It is one of the most luminous in the class of so-called Cepheid variable stars. Its average intrinsic brightness is 15,000 times greater than our Sun’s luminosity. Image Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-Hubble/Europe Collaboration

RS Puppis rhythmically brightens and dims over a six-week cycle. It is one of the most luminous in the class of so-called Cepheid variable stars. Its average intrinsic brightness is 15,000 times greater than our Sun’s luminosity. Image Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-Hubble/Europe Collaboration

Well, you’re absolutely right that radar is an ideal way of measuring distances to objects; with radar you bounce a radio or microwave pulse off of the other object (a planet, for instance) and wait for it to come back. The Arecibo Observatory in Puerto Rico is one of the best observatories...

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