Why do we age over time? | by Sarah

Recently, Hilda Clulow passed away at a great age of 111, she was the UK’s oldest person. She was born on 15th March 1908 and witnessed momentous events including the discovery of antibiotics, the moon landing and the release of the first iPhone. It is unlikely that many of us will live to this great age, as the average life expectancy in the UK is only 80 years old, which is 31years less than Mrs Clulow’s record age.

Why even with improvements in medicine, is this? This is one of the unanswered quest ions of modern science. We still do not have a conclusive reason why with the passage of time our bodies age. Scientists have come up with many theories why our bodies biologically age, however, the common theory is that it is a combination of factors and not linked to one single cause.

One theory states that over time as our cells divide mutations accumulate and this accumulation can cause problems for the human body. On average, a human cell will divide between 50-70 times before cell death. There are trillions in our body so it is likely that some cells will not replicate correctly leading to mutations in our cells. Mutations in cells can also be caused by mutagens, for example, ultraviolet radiation. Most of the time, the mutations are harmless and DNA repair mechanisms fix the damage, but errors can slip through as we age. Ageing has been linked to the deterioration of these DNA repair mechanisms. This deterioration allows for permanent errors to become more common as we grow older. If the cell with mutated DNA is not corrected then, they can pose a health risk, for example, tumour cells contain a mutation which affects the cell’s genes which control cell division causing them to divide uncontrollably. This risk increases as we age due to the deterioration of the DNA repair mechanisms.

If a cell’s DNA becomes too damaged it will enter apoptosis where the cell dies at a programmed rate or the cell will become senescent. Senescence is a process where the cells kill themselves or become nonreplicating and become dormant.

However, it has been suggested that an accumulation of these cells can speed up cell ageing by releasing inflammatory cytokines (small proteins that are important in cell signalling). This is thought to contribute to atherosclerosis, a disease in which plaque builds up inside your arteries, and other ageing-related diseases. This theory states that ageing is directly affected by the damage to cells over time during division.

Another theory was developed in the 1950s by Denham Harman. It is known as the free-radical theory of ageing and states that ageing is caused by the accumulation of damage inflicted by reactive oxygen species (ROS). ROS is produced in all aerobic cells and is formed from products of oxygen. It can be beneficial to organisms as cell regulators, but in high doses, they become cytotoxic, often leading to cell death. Our cells’ levels of free radical damage increase with age and this has been linked to an increase of ROS over time. The free radical theory may also be used to explain many of the structural features that develop with ageing including DNA damage and a decline in mitochondrial function.

However, in the 1990s, scientists studying model organisms observed phenomena that contradicted the free radical theory. They showed that the enzymes that block the product ion of ROS didn’t extend the lifespan of mice. They found in worms, stressing the mitochondria at a certain stage of development actually increased life span. So we are still unsure whether this theory serves as an explanation to the main reason why we age or is just another factor of ageing.

A final theory states that ageing is due to an accumulation of our cells which lose the ability to replicate correctly. Our DNA strands become slightly shorter each time a chromosome replicates itself. Telomeres help prevent genes from being lost in this process but this means that as your chromosomes replicate, your telomeres shorten. An enzyme called telomerase helps prevent too much damage to your cells. This includes shortening of your telomeres. Telomerase does this by adding additional telomere sequences to the ends of your chromosomes. However, telomerase is only found in certain cells so most cell types in your body don’t have telomerase. This means that most of your telomeres continue to get shorter over time so the DNA polymerase cannot fully replicate the ends of chromosomes in most cells. If the telomeres shrink too much or are damaged, cells enter senescence. This slows the body’s ability to renew itself. Telomere damage has clear effects on ageing. Mice with short telomeres have diminished life spans and reduced stem-cell and organ function, while mice whose telomerase is enhanced in adulthood age more slowly. In humans, mutated telomerase is associated with disorders involving organ dysfunction and elevated cancer risk.

Yet even with all these theories we still have not got an answer exactly why these factors occur and how they function together. Maybe in the future, we will have conclusive proof of why, over time, our body ages, but will that take a couple of years or a couple of lifetimes to find. I guess we will have to wait and see what momentous events we will witness.

What’s inside a black hole? | by Lexy

Black holes were first theorised by John Michell in 1783. He named them ‘Dark Stars’. At that time, it was a common belief that light was made up of particles which reacted to gravity. Michell believed that these so called ‘dark stars’ were very large stars with a very strong gravitational field, so strong that no particles could leave, including light particles. This meant that ‘dark stars’ would be invisible to the human eye.

Progress was not made on the theory of black holes and dark stars until the 1900s, when Albert Einstein started work on his theory of general relativity. His theory stated that space and time were different directions in ‘space-time’. This was then bent, creating black holes.

The current theory of black holes came from John Wheeler in 1967. They originate as stars, formed when stars begin to die, cooling and shrinking, increasing in density, until it becomes a concentrated mass that bends space-time, punching a bottomless hole through it. The smaller and more dense the mass, the stronger it’s gravitational pull, eventually even light cannot escape. The Event Horizon is a point where the gravity is just strong enough to drag light backwards. Past this boundary, light can escape, meaning we can see up to, but not beyond, this point. Nothing can travel faster than light, so if light cannot escape the black hole, nothing else can. However, if you are beyond the event horizon, it is possible to resist the gravitational pull, albeit with great difficulty.

The stark lack of light is just as eye catching as a bright light. A black hole appears as a black void, in which nothing can be seen, not even a slight outline. Space is always lit up by stars, and so a sudden gap in light is noticeable.

The size of a black hole relates to how much matter is in it. A larger black hole contains more matter. Due to the uncertainty relation, a concept imagined by Werner Heisenberg in 1923, some particles are able to escape from a black hole, despite the fact that nothing can travel faster than the speed of light. The uncertainty relation means that with sub-atomic, and atomic sized objects, such as the particles in black holes, it is impossible to tell more than one aspect of its movement accurately. If the exact location of a particle is known, the exact speed cannot be known and vice versa.

In smaller black holes, the location is known, so the speed can only be estimated, and varies to a certain degree. This then makes it possible for particles to move just over the speed of light, despite what anyone’s ever been told about light being that fastest thing to ever move. Anything moving over the speed of light has the ability to ‘outrun’ the gravity that is pulling it back into the hole, meaning it can escape past the event horizon. Inside a black hole, the most popular theory is of a singularity. The remains of the dead star, once it has finally stopped shrinking. Atoms, in their common state, are mainly empty space.The gravity in a dying star becomes so strong that it causes these atoms to collapse on themselves, leaving no space, either between that atoms and within the atoms. This is the densest an object can ever become, and since the atoms no longer exist as atoms due to them losing their atomic structure, the singularity has no specific material or chemical elements.

It has been theorised, that in seeing the singularity, it would be possible to avoid hitting it and being compressed to become part of it. In simpler words, it would be possible to avoid being squashed to death. Instead, one could almost swim past it, falling through a wormhole. These are disturbances in the fabric of space-time. By falling through one, you would end up in another area of space-time; a different place, a different time, or both.

Some original uses of black holes appeared in fiction writing long before the idea had been properly investigated by scientists. To start with, they were imagined as ‘monsters’, the villains in a story that would consume anything near it. They may also travel through space, eating anything in it’s way. They were ‘vacuum cleaners for the universe’, often sucking up nearby stars and planets, and the occasional unlucky astronaut or space-explorer.

Later, they were adapted into wormholes, used as portals for people to travel between different places, galaxies and sometimes even universes. Being able to travel faster than light became a common occurrence, with both dystopian and utopian novels using wormholes as the futuristic method of transport. Sometimes, characters would appear in unpredicted places, however star-gates were also made, where each wormhole had a partner that linked to each other, much like a doorway between different sides of the universe.

They were also used as a method for people to travel in time, being able to see the future and travel to the past. This attribute could be used for both good and bad characters, used to fix the future or to change the past.

Featured image: By Event Horizon Telescope – https://www.eso.org/public/images/eso1907a/ (image link) The highest-quality image (7416×4320 pixels, TIF, 16-bit, 180 Mb), ESO Article, ESO TIF, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=77925953