How do you know that the universe is expanding instead of all matter shrinking?

Answer 1

I'll turn the question back on you: what would be the observed differences between a shrinking matter universe and a growing space universe?

Your theory would have to account for the redshift (somehow, shrinking the photons has to be interpreted as redshifting them). At best, you'll probably come up with a theory which predicted the exact same stuff as the standard model. And what is the point of that when the standard model works just fine.

If you can come up with a theory that explains the current observations and has some testible prediction that differs from the standard model, then physicists will be interested in hearing it.

To answer Elliot's question:

We know that the redshift corresponds to far away stuff because we have standard candles to measure by. For example, certain types of stars pulsate, and their actual brightness is proportional to their frequency. Consequently, when we see one of these, we can determine about how bright it really is. By comparing it's actual brightnes to its percieved brightness from earth, we can calculate roughly how far away it it. We can also measure its redshift. It turns out that redshift is directly correlated to distance, so from that, we deduce that the universe is expanding. Another bit of evidence the cosmic microwave background (which is light from when the universe was very young and made up of plasma, and has been redshifted all the way into microwaves).

Answer 2

Well its a theory, but based on these observations of how light travels in space it suggests that the universe is expanding. How this works is by Hubble's constant which describes how the color of the light (wave length) actually changes and becomes longer as the distance becomes farther from the observer. For example, in extreme scenarios the light will go from visible to what we can see with our eyes to infra-red which is below our spectrum of sight. This suggests that the light had to travel a significant distance. But how do we know that its expanding rather than the star is just really far away? My guess is that there most of been a lot of observations over a span of time that showed some change.

Answer 3

:-) it fairly works... If rely have been shrinking., then, as you assert, the mentioned info might nevertheless slot in nicely with this theory. we would not be conscious the version, because of the fact our metrics may well be shrinking on the comparable fee, and it would slot in nicely with gentle having a relentless velocity (in vacuum). And customary rigid bounds do not influence it - no extra desirable than they influence the assumption of an increasing universe. it fairly is all relative, as Einstein might say. (sure, I had the comparable theory whilst i became lots youthful, and on no account had all of us be in a position to disprove it.

Answer 4

by the red shift, which works like the Doppler effect,
the best way to describe this is with an ice cream truck,
when the truck is coming toward you the music sounds crisp but once it passes you is sounds like some creepy horror film music, same with light waves, as something moves away its light moves or "shifts" toward the red end of the spectrum

Answer 5

The Doppler effect.

http://tech.groups.yahoo.com/group/NeatAstronomy/

Answer 6

redshift/doppler effect. God I love science, I want to become the smartest person alive and take over the world. And then get all the money, power in the world.

Answer 7

The Big Bang theory was wrong. It started out slow, like a bag of popcorn in a microwave. It is no longer expanding.

Answer 8

When did I claim to know this?

Answer 9

you can calculate how fast the universe is expanding thanks to the hubble telescope