# Theoretically if the Tengen Toppa Gurren Lagann is 10 million light years across, it would mean that its eventual battle with the equally large Granzeboma would last several billion years, considering that nothing can exceed the speed of light. This would mean that swinging an arm alone might be a feat that would traverse several million light years, which will require the same number of years in real time, to execute. However, since relativistic physics are taken into consideration, it would mean that the Tengen Toppa Gurren Lagann experiences severe time dilation effects that would theoretically make what seems to be a billion years last only several seconds, if the battle occurs at near light speed. Thus, the battle shown might be a condensed event that occurs not from the observer's objective time frame, but from the Tengen Toppa Gurren Lagann's subjective time frame. If the battle really took several billion years though, in actuality, the galaxies should dwindle in terms of their stellar intensity due to the end of solar rebirth cycles caused by the heat death of the universe, assuming a situation whereby a big crunch does not happen.
# Also, if the battle between the Tengen Toppa Gurren Lagann and the Granzeboma really did occur at such an immense inter-galactic scale which also caused several Big Bang level explosions to occur while they were hurling entire gargantuan galaxies at each other, the number of civilizations that they might have destroyed in the crossfire might have been several billion, assuming that a typical galaxy holds about 1 million intelligent civilizations. If each civilization has an upper bound of 1 million people (which will be destroyed by the anti-Spirals if that is reached), the number of casualties in the "duel" between the two giant battle bots might have not just been 1 (the death of the Anti-spiral collective consciousness), but several thousands of trillions. If the battle really did last for several billion years, it would give ample time for more intelligent races to evolve, thereby increasing the number of such civilizations by up to ten-fold, making the number of casualties even more staggering.
# Also, since nothing can move faster than the speed of light, it would mean that information being relayed from the movement of the body parts of the Tengen Toppa Gurren Lagann would take nearly millions of years to reach its controllers, since the light from it would need to cover that amount of distance. In reality, the pilots controlling it will feel immense space-time distortions on their screens, due to the unsynchronized information feedback from different body parts (i.e it takes far longer for light from the leg to reach the eye, then it does for a hand placed in front of the face). Unless time dilation reduces its effect dramatically, Simon would not be able to see the enemy and react almost "at the same time" to execute evasive maneuvers. It must necessarily be true that there is a fastest possible speed (such as the speed of light in our universe) in the physics of Gurren Lagann, attributing to the nature of Black Holes and the Spiral Nemesis. If something could travel faster than light, there would be no black holes, and thus no Spiral Nemesis could occur. If there is a fixed maximum velocity, there must necessarily be time and gravitation dilation, suggesting that the battle indeed lasted billions of years.
# Considering that the battle took place with so many Big Bang level explosions with inflationary powers that might introduce a lot new mass into the universe without any averse side effects, it is possible that the universe that Gurren Lagann was in, was a universe with a low cosmological constant; meaning that the universe was probably open and susceptible to a possible heat death by expanding ad infinitum. Introducing so much additional mass into the universe might have increased that constant, and caused it to become flat, meaning that it will expand, but only up till a certain point, but never contract. On the other hand, it may have become closed, meaning that gravitational energy exceeds thermodynamic energy, which will eventually cause it to collapse onto itself again to form a Big Crunch, and the dreaded Spiral Nemesis before that. If that is the case, it would occur that the Spiral Nemesis might never have been possible until the Super Tengen Toppa Gurren Lagann's final battle, which unlocked its possibility. Nonetheless, one possible way of avoiding an infinite Spiral Nemesis in which another Big Bang can never be created is to possibly create more mass to increase the surface of the super massive black hole formed, to increase the chances of quantum mechanical activity causing quantum tunneling to cause the black hole to evaporate through the formation of virtual particle-antiparticle pairs. This would allow some mass to escape in the form of energy, in which sentient races can use to their benefit. Of course, theoretically, for a black hole the size of the universe to evaporate through quantum tunneling processes alone, it would take several trillion to the power of several hundred years. This means that the Spiral Nemesis, while unavoidable in certain situations, will eventually undo itself and cause the universe to be reborn in a cyclical process. Avoiding a Spiral Nemesis and a heat death is also possible if intelligent life interferes with the direct cosmological process of the universe by using their spiral energies to balance the amount of mass in the universe by shifting them from one side to another to avoid increased entropy, and by stop creating too much mass.
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