# What happens if 1 cm of Cosmic String impacts Earth?

I have seen in different science fiction use Cosmic Strings (1-dimensional defects in spacetime) as weaponry, and it made me interested to make the most feasible way to weaponise them. Of course, I understand that Cosmic Strings are extremely dense, with a few inches being able to weigh as much as a mountain. So, it is unlikely that they can be used as a cutting weapon.

So instead, I had another idea to weaponise them, that sounds more feasible. I imagined a satellite inbuilt with multiple high-power particle accelerators that can accelerate and collide particles to the point that the surrounding space becomes as energetic as it was during the electroweak (or even GUT) epoch, and through spontaneous symmetry breaking, creates the cosmic string. The cosmic string is (roughly) 1 cm long, and immediately as it is created, it descends down to Earth like a meteor or a rocket going through re-entry.

Surely such a cosmic string would bear insane amounts of kinetic energy. But what would be the specific effects upon collision with the Earth? Just what happens?

PS: Do not ask too much about the accelerators. Just assume they have enough energy to even emulate the electroweak or GUT epoch. Oh, and I heard about the accelerator problem, so I use some unobtainium to make these accelerators handheld, alright?

• If you have enough energy available to create a cosmic string, which you intend to immediately use at orbital range, it would be far more efficient and less dangerous to you to just use it to power a laser... or fire a bullet. Commented Dec 15, 2020 at 2:49
• Keep in mind that if you have enough energy to produce something with the mass of a mountain, your satellite will require battery/capacitor banks massing many millions of mountains. Commented Dec 15, 2020 at 2:50

I suspect your estimate of the mass of a cosmic string is ever so slightly off. The figure I remember is approximately the mass of a galaxy per centimetre. The source is J Richard Got III's Time Travel in Einstein's Universe: The Physical Possibilities of Travel Through Time (London: Weidenfeld & Nicolson, 2001).

In this case, the cosmic string will not fall like a meteor to Earth. Instead Earth, the Moon, the other planets of the solar system, and the Sun itself fall towards the cosmic string. The gravitational mass of a galaxy concentrated in the length of one centimetre will do things like this.

It won't end well. But you knew that.

As weapons go, this one is great for wiping out entire planetary systems. You only need to have the sort of particle accelerator that simulate and stimulate the GUT Epoch in a confined space. Not easy, but who said annihilating solar systems was going to be easy. Forget merely destroying planets this would do so much more.

• with such mass i would add also, to the problems, event horizon measured in ly's as its diameter goes Commented Dec 15, 2020 at 8:18
• @MolbOrg Lightyears? Our central black hole has an event horizon light-minutes across and it's got a significant chunk of the galaxy's mass in it. Either way, the scenario would just be the Solar System being consumed by a SMBH. Commented Dec 15, 2020 at 10:37
• wikipedia says: A cosmic string about a kilometer in length may be more massive than the Earth. However general relativity predicts that the gravitational potential of a straight string vanishes: there is no gravitational force on static surrounding matter.
– ths
Commented Dec 15, 2020 at 15:36
• @ths But only for straight straight strings, any kinks or bends and gravitational force is exerted by the string on surrounding matter. I do tend to preference scientist over Wikipedia as a source of information, but if there is more up to date information I'm willing to consider that. Commented Dec 17, 2020 at 7:50
• @Starsong67 indeed, I overestimated things a little, the radius of event horizon for milky way seems to be about 0.4684 ly, so the total is close to 1 ly but isn't multiple of ly's Commented Dec 19, 2020 at 1:07