We’ve had a lot of requests to host a proper forum to discuss space, from opinions on All About Space magazine to just something interesting you want to tell us. So now, on a regular basis, here on spaceanswers.com we’ll be posting your best emails, letters, and comments. If you’ve got something you want to say you can email us at firstname.lastname@example.org or check out our ‘Contact Us‘ page to see other ways to get in touch.
When looking at a far off galaxy and the light takes, for example, 113 million light years to reach us and we look for a planet the could be habitable, how do we know that in the time the light took to reach us life hasn’t evolved on it?
There’s no way we can know for sure Rick. Obviously most things we look at in the night sky are many years older now then when the light is reaching us. However, if we find habitable planets, it doesn’t matter how old they are – at least we know there are habitable planets out there. Now we’ll just have to work out how to get to them…
Richard Simpson, East Sussex
In issue 13 of All About Space on page 22 it states the speed of anything in the universe is limited by the speed of light (186,000 miles per second). It says nothing can travel faster than this. Then on page 80 in the Quick-Fire question, it says “Is the Universe expanding faster than the speed of light?” with the answer “Yes! The Universe is expanding faster than the speed of light.” Can you shed some “light” on this for me please?
Thanks for the question, Richard. We agree that it can be a bit confusing! The universe can appear to be expanding faster than light because, relative to each other, two galaxies are moving away from each other. So, for example, our Milky Way might be moving away from a distant galaxy as it also moves away from us, making it seem to travel faster than light. In reality, though, it is just our perspective; nothing that we know of can actually move faster than light.
I thought I’d share this artwork that I created in memory of the shuttle programme. I enjoy doing a lot of space art and I thought you guys might like it.
We certainly did enjoy that David, an excellent piece of artwork. Now, get to work drawing every other spacecraft. We want to see more.
Claire Armstrong, Scotland
I would like to know if there are galaxies in the universe that are coming towards us as well as moving away from us (apart from Andromeda M31). When I look at the Hubble Ultra Deep Field and other pictures it appears as if some galaxies look quite red and others appear to be blue (although some can also appear to be green so this may all be pointless). But I was just wondering if the ones that appear to be blue are moving towards us and the ones that appear to be red are moving away from us, as in redshift? Or am I just totally misunderstanding the whole point of redshift?
What you’re actually observing here is the spin of the galaxy, and it’s how we discovered that galaxies are spinning. The side of the galaxy that’s spinning towards us is often blue shifted, whereas the side that is moving away from us is redshifted.
However, there are also a few hundred galaxies that we know of that are blueshifted because of their motion. Most of these are found in our Local Group and, as you say, they are moving towards us, as most of these galaxies are orbiting each other. Blueshifted galaxies moving towards us are quite rare otherwise, though.
Bear in mind that a blueshift doesn’t mean they’re coming straight at us. They might just be moving past us, or vice versa. The only galaxy we know that’s going to collide with us is, as you say, Andromeda M31.
Chris. H, Perth, Australia.
Hi my name is Chris, I love your magazine and it makes me wish I chose a different profession. I was just curious as to what theories or speculations there were on how Europa first acquired the water it has and also how it would have maintained its structure in its early stages?
Thanks for the question Chris. Hopefully you checked out our feature on Europa in issue 15 of All About Space. Europa is believed to have acquired and maintained its water by the constant melting and refreezing of the ice on its surface. Its eccentric orbit around Jupiter causes tidal heating, and this is thought to be responsible for melting ice beneath the surface. While parts of the subsurface ocean likely remain as water, it is the parts closer to the surface that go through this cycle of melting and freezing. Who knows, though? Perhaps there are more secrets of Europa we are yet to uncover…