A question for a cosmologist about brane death

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The “string theory revolution” began in 1984 and I graduated with my astrophysics degree in 1987, perhaps unsurprisingly, having been taught nothing about it at all.

But now, reading The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos, (a good book) I discover that we may all be living on a brane – a three dimensional slab of reality “floating” inside ten dimensional space. And indeed there may be many of these branes perhaps just milimetres away from all of us, each of which might appear to its inhabitants (if its physical laws allow for any inhabitants, of course), as a fully dressed universe in its own right.

Now, so the theory goes, photons and indeed all particles of the electroweak or grand unified force (assuming it exists) cannot move between the branes, but gravitons, the theoretical (and undetected so far) quantum messengers of the gravitational force can. Indeed this ability of gravitons to stray into other dimensions is what is believed to make the gravitational force seem so weak to us.

But what if a highly massive object in another brane were to pass close by us. Such an object could have a very strong gravitational field that we would feel in this universe/brane and which could have drastic effects, perhaps putting us all at risk of “brane death”. Couldn’t it?

Well, I suspect I have misunderstood the mathematics of this. The fact we don’t see galaxies ripped to pieces by the super massive black holes at the centres of galaxies in other branes is rather more likely to lead me to believe that I have missed a point about how this works than to conclude the theory is that easily disproved.

Perhaps a reader might enlighten me?


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