http://www.spaceref.com/news/viewpr.html?pid=32078

An interesting read.

One question though, does antimatter react with light? If so surely the detection of it would cause its anihilation?

I guess you shine the beam the other way. That way the antiparticle won't notice.

I don't think there's any such thing as an "anti-photon", so no more so than normal matter.

There's an anti-everything, because in quantum physics everything is just maths. Theoretically, an anti-photon is a photon that is traveling backwards in space time (since a photon is defined by a wave traveling in space time, an anti-photon is defined by a wave traveling in the opposite direction). A photon is not matter, therefore there's no reason for it to interact with anti-matter to cause annihilation. A photon and an an anti-photon would in theory interact with each other but as far as I know we haven't made anti-photons yet. It may not even be possible to do so in the 'normal' universe. Its almost certainly extremely tricky to get a photon and anti-photon in the same place at the same time, because you would have to create the anti-photon after it was annihilated, from our perspective.

Hmm.. a bit of further reading does suggest an anti-photon is impossible to create in our universe. In our universe, photons are created when a subatomic particle changes quantum state and has to 'dump' energy to do so and that energy doesn't have a 'sign'. It's just considered to be positive because it's emitted. To create an anti-photon you would have to get a subatomic particle to take in energy and emit an anti-photon in doing so, which obviously doesn't happen. The particle changes state and jumps to another quantum 'band' when you pump energy into it, but doesn't emit anything. Theoretically, an anti-photon is possible but I think it may impossible for them to actually exist.

Jon

They sound like the theoretical tachyons which have properties similar to the anti photon.

You can't have an anti-photon because a photon isn't a particle - it's an electromagnetic wave that just happens to exhibit particle-like behaviour (wave-particle duality). Anti-matter, as it's name suggests, is the the anti-particle equivalent of normal matter, so unless someone finds that photons have mass (which is impossible because by Einstein's law E=Mc2, a particle travelling at the speed of light would have infinite mass, which is clearly impossible as I can quite clearly see what I'm typing ).

However, bare in mind that the observable universe may or may not have had different rules, depending on your place and time within it.
Short version - laws of physics aren't, or at least only applicable here and now.

Also, light does indeed have an effective mass (or at least weight within a gravitational field) which has all the properties you expect from Mass. Photons 'fall' in response to gravity, after all.

Yup, general relativity says so

Let's be specific.

According to GR, light goes in a strait line. It's space that is bent.

Science is still not mature. There are many contradictions and mysteries to be solved. General relativity and quantum mechanics are quite uncomfortable when you put them in the same room.

I really hope I can retire while my brain still half works so I can catch up on the last 50 years of development

I was not thinking before. The photon is its own anti particle. Einstein basically said that it was impossible for an object to cross the light barrier. There are hypothetical particles called tachyons that travel faster than the speed of light but need energy to slow down, in the same way that you need infinite energy to speed up to the speed of light they would need infinite energy to slow down to the speed of light.

And that's why Sci-Fi geeks get so excited about black holes.

Special relativity gives a discontinuity at the speed of light. General relativity gives a discontinuity in a black hole. If you could pass through a singularity... oh wait, there's a couple of films about that

I still would not want to try and get anywhere near a singularity, annulus or not. Spaghettification is going to be a problem. If you managed to find a way around that problem then flying through the centre of a annular singularity will take a lot of skill.

The only way to control spaghettification (surely my favourite scientific term) is to be able to control the force of gravity within a localised area i.e. have some sort of field or bubble that keeps your ship at 1G as you approach the event horizon.If you can do that you probably don't need all that tedious mucking about with black holes anyway, because if you can do that you can do pretty much anything.

IIRC in the Star Trek universe, the PSB for FTL travel is they don't actually go faster than light, they use a localised effect field to increase the speed of light in the immediate volume of space around the ship, thus allowing it to travel faster than C without breaking 'the rule'. If you can produce localised gravity, you can probably pull that trick as well.

http://www.generalnonsense.net/showthread.php?t=4380

The trick, as they say, is to do this without destroying the ship and everyone on it.

Star Trek gets round this with an inertial dampening field IIRC.

Ah yes. there's a famous old video game called, coincidentally, 'Gravity' that uses a similar thing. Essentially you create a gradient of gravity along the vector of travel, so you're basically always falling forwards and therefore accelerating. Obviously, if you do it too violently your ship falls to bits.

The game was fantastic. It represented the universe as the well known space time rubber sheet, with planets and stars creating 'dents' you had to fly round. And IIRC they did use black holes to travel long distances. One of my favourite games of the period. especially when you got the bomb that could turn a solar system's sun nova .