"Can you build a time machine?" "The answer is yes" Professor Cox said.
There's just one small problem, says Cox – if you can build a machine capable of time-travelling, you can only travel into the future. You can't come back.
Professor Cox also suggested that research at the LHC could uncover additional dimensions - thus, perhaps finally understanding how the TARDIS is bigger on the inside.
Professor Cox says that time travel is possible, and has already been done - albeit on a very small scale. The technology does not yet exist to accelerate something as large as a police box to almost the speed of light.
Professor Cox says that, armed with such technology, “you can go into the future; You've got almost complete freedom of movement in the future". he added.
To "travel" forward in time, you just need to accelerate closer to the speed of light, Cox says — as you approach that speed, time slows down, just for you but according to Einstein's theory of special relativity.
“If you walk fast, your clock ticks slower than stationary people. As you approach the speed of light, your clock slows down so much that you could travel 10,000 years back into the future" Professor Cox said.
Cox previously stated on Conan O'Brien's chat show that traveling into the past was "impossible". "You can travel into the future as fast as you want. You can't travel into the past" he added.
But in his speech in Birmingham, the physicist elaborated more – suggesting that the "wormholes" often used in science fiction as portals through time may not provide an easy way to travel into the past.
“In general relativity, you can do this in principle. It has to do with the creation of these things called wormholes; Shortcut via location and time. But most physicists doubt it. Hawking came up with the 'chronology protection conjecture' – the physics we do not yet understand means that wormholes are not stable'.
However, traveling between different dimensions could be easier – a relief to the Doctor, for whom "transdimensional engineering" was an important part of the TARDIS.
Cox says, “We look for extra dimensions at the LHC. You can imagine extra dimensions in space, and we are living on a sheet of higher dimensional space.