how can you say that the universe expanding?how can you say there is another galaxy?

Answer 1

well, there is proof of another galaxy.. tons of other galaxies. You can see some with a telescope. Ever heard of Andromeda,not fake! :) the universe is expanding in its own way

Answer 2

This was a major question in astronomy in the 1920s. At the time there was considerable conjecture over whether the "spiral nebulae" were features at similar distances to the stars we can see or whether they were "island universes", that is collections of stars at much greater distances.

This was the context in which Edwin Hubble made observations of the Great Spiral in Andromeda using the new 100 inch telescope. This instrument was able to resolve the Great Spiral into individual stars. Observing the stars, Hubble was able to identify a particular class of variable stars known as Cepheids (after the defining star Delta Cephei in the constellation Cepheus.) The period of the variability of such stars is believed to be related to the absolute brightness of the star. This was based on work over the preceeding two decades by the women computers of the Harvard Observatory. Armed with a value for the absolute brightness of a star the measured apparent brightness implies a distance based on the inverse square law of light intensity. Hubble's observations of the Cepheids indicated that the Great Spiral was considerably further away from us than other stars and globular clusters, suggesting that it was indeed an independent island universe, which we now call a galaxy.

As more observations were made of other nebulae, they too showed large distances. Observations had also been made of the spectra of nebulae which showed a noticeable reddening, that is a shift of spectral lines towards the red end of the spectrum. Collecting together the distance determinations from Cepheid variables and the spectral red-shifts showed that the red shift was proportionally greater for objects that were further away. This implied that the Universe as a whole was expanding with objects a greater distances from us receeding at ever greater speeds.

The realisation of these implications in the 1930s provoked Einstein to say that he'd made a major blunder by introducing a cosmological constant into General Relativity to keep the Universe static. The theory had naturally implied either an expanding or contracting Universe.

Answer 3

There are over 200 billion galaxies that we know of.
Light travels in a red shift when an object is moving toward us and a blue shift when it is moving away from us.

When we look at galaxies outside of our local group the galaxies of the universe are blue shifted, and moving away from us. This it easy for scientists to measure with spectrometry and they can see the expansion is accelerating.

The Andromeda galaxy is the closest one to us at about 35 million light years away and it is huge. From a good dark sky site away from city lights on a clear night you can see it without a telescope however it appears like a hazy cloud four times the size of our moon.

I am an astronomer with a very powerful telescope (Meade RCX400 12") and I've seen hundreds of galaxies. Using astrophotography, I can see galaxies of a magnitude of >18 which means I have seen by long time exposure galaxies that are over 8 billion light years away.

Many years ago before the airplane we once believed the Milky Way was the universe. Now we know better.

Answer 4

We can say there is another galaxy because you can SEE it plainly in the telescope. A big galaxy sitting there in the sky. We named it M31, or the Andromeda galaxy.

We can say the universe is expanding because the light from distant galaxies is red-shifted. This red-shift occurs when objects are traveling apart at high speeds. We see that the furthest galaxies are moving away from us at the highest speeds. This strongly suggests the universe is expanding.

Answer 5

The above users post about the Doppler effect is correct on the issue with expanding universe.

I think you might mean "how do we know there isn't another universe"? This is considered a big issue and there are other theories such as the M theory that describe other universes.

If you did mean galaxies then yes this is obviously easy to see because of Hubble's images.

Answer 6

We know the universe is expanding beacuse of the doppler effect. You know how the tone of a train whistle changes as it comes towards you? Well, the same thing happens to light. We have measured the change in light frequencies in far off stars and determined that they are travelling away from us. The only explanation for that is that the universe is expanding.

As for other galaxies, look up at the sky at night :)

Answer 7

I have actually seen other galaxies. It is possible to see the Andromeda spiral without even using a telescope. But with a good pair of binoculars or a telescope, it is possible to see dozens of other galaxies.

As to how we know the galaies are moving away from us: look up the Doppler shift.

Answer 8

Try and knock and ask Genesis.
Been waiting out there for centuries.
But no one come and passing by.
Ever wonder how the blind were blindly following the blind?
Luke 6.39-40