Questions Show: Ice in Space, Expansion of the Universe, and Death from the Skies

Another week, another batch of questions. If ice disappears in your freezer, how can it last in space? How can the Universe be expanding faster than the speed of light? And what is the risk from a coronal mass ejection in an airplane? All this and even more questions. If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

Ice in Space, Expansion of the Universe, and Death from the Skies

Stellarium Software

If ice disappears in your freezer, how can it last in space?

• Sublimation of ice — USGS
• Ice in craters on the Moon? Latest data says no — Universe Today
• Water and ice in the universe

Are objects moving away from us faster than the speed of light?

• How Can Galaxies Recede Faster Than the Speed of Light? – Universe Today
• The Expanding Universe – SDSS
• How fast is the Universe expanding? — NASA

Are people in airplanes subject to more radiation from a Coronal Mass Ejection blast?

• Cosmic Radiation and Airline Crew Radiation Exposure – Astroprof
• Coronal Mass Ejections (CME) – Windows to the Universe
• Solar Maxiumum — GSFC
• Primer on Space Weather – NOAA

Will the Sidereal Day and the Solar Day ever be the same?

• Sidereal Day -- World of Astronomy
• Solar Day – World of Astronomy
• Timekeeping:  solar day vs. sidereal day — UTK
• Is Earth's rotation slowing down? — Physics and Astronomy Online

Does light have mass?

• Does light have mass? – Discussion on BAUT Forum
• Does light have mass? — Cornell University
• How gravity affects photons – GSFC
• Characteristics of a photon — Play Hookey.com
• E = hv = hc/lambda
• And Einstein's famous E = mc^2

Does the Coriolis Effect affect how water drains?

• Coriolis Force – UIUC
• Bad Coriolis – PSU
• Read Phil Plait's first book "Bad Astronomy" – he devotes an entire chapter to the Coriolis Effect

If a large asteroid hit the moon in just the right way, could the moon hit the Earth?

• Asteroid Ceres – Planetary Society
• Program to calculate the effect on Earth from various sizes of impacts — U of AZ
• Discussion on this question on Physics Forums

Does dark matter decay over time?

• Dark Matter – Berkeley U
• Grand Unified Theory – Particle Adventure
• Proton Decay – Wiki

1. jason white Says:
   November 10th, 2008 at 1:27 pm

   I have a question. Taking into consideration fractals (eg. the atom, the solar system, and galaxies) why is it you think the universe is expanding at all? everything seems to revolve around a central core. The galaxies if rotating along with us then only 2 things can be happening. Either the galaxies are far (toward the outer edge) or near (along the inner edges) and therefore as we rotate along with them we are either approaching them or we have passed them and moving away from them. This would easily explain your red shift. Lets take for example Jupiter. in the night sky as our orbit approaches the orbit of jupiter the red shift will change as will the shift change as our orbit passes juipter and instead of approaching jupiter we are now moving away and thus shifted more towards the red. unfortunatelly the millions or billions of years it would take for the actual shift to change (in a galaxy) would be hard to actually observe. so again back to my question. How is it you know the universes is actually expanding.

2. Sci-Fi Si Says:
   November 10th, 2008 at 4:28 pm

   @Jason

   A.

   We say the Universe is expanding because in every direction we look, the stars and galaxies are in red shift (the normal wavelength of light has been stretched on it's journey to us). This measurement of the amount of red shift is not linear to the measurement of the Galaxies distance. This applies on a Universal basis.

   Matter does have a habbit of 'clumping' together through gravity and it would be true to say that Andromeda, our nearest Galaxy is actually moving toward us. Though it will take billions of years before our Galaxies collide. On a Galactic level Andromeda is closing in on us, but on a Universal scale, Galaxies in all directions are red-shifted and moving away from us in all directions.

   We know the Earth is not in the centre of the Universe and that we inhabit an outer spiral arm of the Milky Way Galaxy; we can say that this expansion is not just local to our area of space but a Universal event.

   We can explain how all Galaxies in general are expanging away from each other with the notion that it is the 'space' between each Galaxy that is expanding.

   Hope that helps.

   Q.

   What I find fascinating is that no two objects can move away from each other faster than the speed of light. However THREE objects can. Object 1 can only move away from it's neighbouring Object 2 at light speed, and Object 3 can move away from it's neighbour Object 2 at light speed.

   The result is Object 1 can not 'see' Object 3 as light speed is insufficient to traverse the distance of expansion beyond the rate of separation of bodies 1 and 3. Thus we have an apparent 'edge' to the Universe.

   If we were standing at the very edge of what Hubble can visibly show us – How much further could we look?

   The mind boggles.

   To briefly go mad, we could state that Object 3 can communicate with Object 2 via light communication; and Object 2 can communicate with Object 1 via light, BUT Object 3 can't communicate directly with Object 1 as the expansion is greater than light speed (unless the information was relayed via Object 2????)

   Bonkers!

   I love this show!

3. P.J.LAKHAPATE Says:
   November 11th, 2008 at 1:18 am

   Question

   What do you mean by "Universe is expanding?"

   Does it mean only going away from each other.

   Or Does it mean more matter is added to the Universe?

   If yes, from where is it coming?

   Pls reply in such a manner that any layman can understand.

   P.J.LAKHAPATE
   plakhapate@gmail.com

4. Harold Says:
   November 12th, 2008 at 7:16 am

   Would love to follow you all on Twitter, but the search feature on Twitter has been out of commission for some time, and nowhere on your 'contact us' page do you mention your Twitter ID's.

   Perhaps you could include that in an upcoming show?

   Thanks,

   H

5. Brad Says:
   November 17th, 2008 at 5:36 pm

   Regarding the question "Will the Sidereal Day and the Solar Day ever be the same?" the answer should have been yes. The Sidereal Day can have the same length as the Solar Day. If the earth rotates at a certain speed so that it takes 2 years for a complete revolution then the solar day should be equal to the sidereal day.

6. jason Says:
   November 26th, 2008 at 7:55 am

   What is it with scientist and thier deal with dark matter and dark energy. There is somthing they think they cant explain and they decide to just give it a label that they invent. What if the universe is much older than people think. We can only see the matter in this universe that still gives off some type of radation. What about all the existing matter that is no longer giving off this radation? is it dark matter? In a sense yes but it does not fit into the description that is currently given or does it? Is the fabeld dark matter just dead stars and pllanets?
   And what about this dark energy? Dark energy sounds like an over active imagination at work. I mean dark energy would be energy that has already been used, since it can not be created or destroyed according to conservation then the energy would just either become heat or actually become matter so why have these people invented dark matter and dark energy?

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