It seems axiomatic these days, especially among the quantum woo set, to call ‘time’ an illusion – a perception. Of course this is scientific rubbish. There’s no question that humans perceive time in many ways, but in terms of physics time IS real, independent of how we sense its passage.
Solar flare of 16 April 2012, captured by NASA’s Solar Dynamics Observatory. Image is red because it wa captured at 304 Angstroms. (NASA/SDO, public domain).
Unlike gravity. That’s the irony, you see. Gravity’s an illusion? Why? Short answer is that the universe is actually weirder than the woo brigade know. Let me explain. According to our friend Albert Einstein, gravity doesn’t exist as a force. Of course, you might have a bit of difficulty imagining gravity is an illusion if you’ve just gone for a gutser down the front steps. But trust me – it is.
Here’s how it works.
Einstein’s Theory of General Relativity – coming up for its centenary and proven to be true, without exception, every time it’s tested – shows that space and time are one entity. A four-dimensional reality with up-down, left-right, forward-back and time.
This space-time fabric is distorted by mass/energy (the same thing in terms of how the universe works). The usual metaphor is to imagine a rubber sheet. Mass/energy can be envisaged as a bowling ball dropped into the sheet. It’ll sag, stretching and curving the rubber.
This rubber sheet, remember, reflects not just space but also time. Consequently, a large mass (or a lot of energy) alters the rate at which time passes. You experience that every day on your phone – its GPS relies on GPS satellites, which have to account for the difference in the rate of time between Earth’s surface and the altitude the satellite’s orbiting at. Time dilation is also caused by the velocity difference between the satellite and Earth’s surface – a function of Einstein’s earlier theory, Special Relativity – which adds to the mix.
GPS works by micro-precise time measurement. If the satellites didn’t take account of Einsteinian frame-dragging, they couldn’t pin the position of your phone to a few metres.
So. Time’s real. What about gravity? Well, that’s the kicker. All-round smart guy Sir Isaac Newton, co-inventor of calculus among other things, identified a relationship between mass and gravity. The larger the mass, the more gravity it has. Simple.
Albert Einstein lecturing in 1921 – after he’d published both the Special and General Theories of Relativity. Public domain, via Wikimedia Commons.
Newton’s theory worked perfectly well, even allowing mathematicians of the early nineteenth century to predict the presence of a new planet – Neptune – from the way it affected Uranus’ orbit. But there were points where it didn’t work. Mercury had orbital characteristics that couldn’t be fully explained by the tugs of all the known planets.
For a while, astronomers theorised there was another world inside Mercury’s orbit – Vulcan. But it could never be found. And then Einstein’s theory came along, and the whole need for Vulcan went away.
Gravity, Einstein explained, wasn’t a force at all. It was a function of mass, sure – but not quite the way Newton thought.
Instead, Einstein calculated, gravity was an effect of the curvature of space-time. Particles would always try to take the shortest route between two places. However, if space-time was curved, they’d be forced to take a curved path. The difference was what we perceived as gravity, an effect intimately associated with mass or – and this is the kicker – energy.
Energy? Sure. Special Relativity showed that mass and energy were different aspects of the same thing (a little mass = a LOT of energy – and go on, you KNOW the equation).
Enough energy, in short, would also distort space-time and, in effect, create its own ‘gravity’. And this was where Mercury came in. The pertubations in its orbit, according to Einstein, weren’t caused by a hidden planet. They were caused by the energy of the Sun itself, acting as an additional distortion in space-time. In 1919 that prediction was borne out when some very precise measurements were taken of Mercury’s position during a transit of the Sun. It was exactly where General Relativity said it should be, if gravity was actually a product of the curvature of space-time.
This was the first proof of the theory – and, as we’ve seen, it’s been shown to be true every which way, ever since.
Gravity, in short, wasn’t a force of itself; it was a function of the way space-time was distorted by mass/energy. This also explained why you couldn’t have anti-gravity, because gravity wasn’t a real force with polarity. It was a structural product of the way the universe worked, but not something real of itself.
The biggest question that came out of this, of course, wasn’t whether gravity was real, which it obviously wasn’t – but why time seemed to move only in one direction. And that’s something that hasn’t been answered. Yet.
Copyright © Matthew Wright 2015