20 b4 twenty: How scientists can come to different conclusions using the same evidence
This is the fourth part of a series called 20 b4 twenty which lays out the twenty issues that every Christian should know before he or she reaches the age of twenty.
So far I’ve stressed that before you reach the age of twenty you need to know…
…that ‘faith’ isn’t blind, irrational, or opposed to reason (regardless of how the dictionary defines the term); and
The fourth thing you need to know before you reach twenty is the key evidence that all scientists must account for to explain the origin of the universe, and the origin of life, the species, and humans, and how scientists come to different conclusions using the same evidence.
As this is WAY too much for one post to cover, I have limited the topic for this post to how scientists come to different conclusions using the same evidence for the origin of the universe as an example (and its still pretty long!).
Last week a commenter to this site said she didn’t know why people assumed that the universe had a beginning. In her opinion, the universe was eternal.
This is a phenomenal statement to make, given how our understanding of the origin of the universe has advanced over the past 50+ years. Nonetheless, I have heard people make this kind of claim before, or variations of it. It is perhaps a misinterpretation or ignorance of the evidence that leads them to this conclusion, or perhaps it is their particular way of interpreting the evidence (more on that later in this post).
In this post, I am only going to list the main pieces of evidence that everyone, regardless of how you come down on the issue of the origin of the universe, has to account for. This is a list of the key findings over the recent past that has lead the vast majority of scientists to (sometimes begrudgingly) accept that the universe must have had a specific beginning (often called the ‘singularity’ – a term I’ll use here) in the finite past.
It is outside of the current scope of this post to explain any of these pieces of evidence in detail. I provide some links to other sites that explain the evidence for those who are interested, but by doing this I do not necessarily endorse everything that is presented in these linked sites.
The evidence for the origin of the universe
Up until the 20th century, scientists overwhelmingly understood the universe to be static (unchanging) and eternal (no beginning and possibly no end).
A series of discoveries changed this thinking:
- Red shift and Hubble’s law which provided (almost, see next point) the first evidence that the universe was expanding (and therefore not static);
- General theory of relativity, which also predicted an expanding universe. Einstein had introduced a ‘cosmological constant’ to his equations to ‘force’ them to not predict an expanding universe. He admitted to adding this constant after observing Hubble’s evidence;
- Cosmic microwave background radiation, which is the thermal energy (remnant heat) remaining after the ‘big bang’ origin of the universe;
- Relative abundance of light elements (hydrogen, helium, and lithium, as well as deuterium), which had no known cause of origin at the present time other than through a ‘big bang’ type of event;
- The fine-tuning of numerous fundamental physical constants in the universe as well as the physical constants. These forces must be just as they are in order for life to exist and we currently have no theory that requires them to be the strengths and ratios that they are;
- Large-scale universal conditions. This set of values that control the expansion rate and uniformity of the universe are also precisely set;
- Conditions that are possibly unique to our solar system (such as the type of galaxy, the properties of the sun, and other aspects of the solar system and the earth itself);
- Radioactive element abundance predictions. Certain existing radioactive isotopes would have decayed if the universe were much older;
- Star formation and stellar lifecycle theories. The star formation cycle uses up more hydrogen than it generates, so if the universe were eternal there would be no hydrogen;
- Second law of thermodynamics (things move from order to disorder, energy gets used up and cannot be created).
In summary, cosmologist Alexander Vilenkin, who himself states that the singularity occurred out of nothing (when there was no time, space or matter) but also believes that we can find a naturalistic origin for the universe, says:
“With the proof now in place, cosmologists can no longer hide behind the possibility of a past-eternal universe. There is no escape: they have to face the problem of a cosmic beginning.”
How scientists come to different conclusions using the same evidence
Here are some of the reasons I have come across to explain why scientists can come to different conclusions about the origin of the universe while using the same evidence:
1. Scientists place more emphasis on certain evidence.
For example, theist scientists tend to emphasize the exquisite fine-tuning of the universe, galaxy, solar system, and earth for life, arguing that these are hallmarks of a mind (a creator). Atheist scientists tend to downplay the significance of this fine tuning, calling it ‘just good luck’ (the anthropic principle). Similarly, there is a debate around the relative importance of some of the physical conditions necessary to support life. If a smaller range of evidence is absolutely necessary to support life, then the probability of life existing elsewhere in the universe is greater (implying that humans are not unique and could have developed without supernatural intervention)
2. Scientists have different a priori commitments to certain outcomes or conclusions.
For example, if you do not allow for anything beyond the natural realm (ie: no supernatural), then you are unlikely to interpret the singularity as the beginning of the universe as this would require something or someone able to create the universe. You rather would identify the singularity as an apparent beginning (not the actual beginning of all matter, time, and space) and attribute the origin of the energy required for the singularity to a different physical source (currently the multiverse theory). (I realize some cosmologists claim that natural laws existed before time and space, allowing them to hop over this line).
3. Different branches of science are based on different branches of mathematics, resulting in conclusions with different levels of certainty.
Historically, physics and chemistry (physical sciences) were based on non-probabilistic branches of math (algebra, geometry, and calculus), although this is changing. This basically meant that testing could be rigorous and fixed solutions could be determined. Life sciences tended to be based more on probability, optimization theory, complexity theory, and chaos theory. In general, the predictions in the life sciences will not be as definitive as those in the physical sciences, and will have more assumptions written into them. The practical application of this is that, as a generalization, we can have more certainty of predictability around questions such as the origin of the universe (physics, astronomy) and origin of life (chemistry) than we can around the origin of species (biology) or humans (anthropology). We therefore anticipate more diversity of opinion in the later two questions.
4. They decide in advance to include or not include certain ‘evidence’.
This might seem like a cheat – adding evidence when I said the above list was all scientists had to play with. But I think its necessary to highlight how proponents of some of the theistic models come to their conclusions. They must account for the evidence listed above, but they also include additional evidence. For instance, Young Earth Creationists will include a literal interpretation (24-hour days) of the Biblical creation account as evidence. Old Earth Creationists will allow a non-literal interpretation of the 24-hour day in Genesis. Atheist scientists will not allow inclusion of the Bible as evidence at all. This decision will necessarily affect their conclusions.
There are surely more reasons than these, but you have to be aware that scientific facts are interpreted by scientists who make judgements about the relative importance and suitability of the evidence that exists. I’m not saying that this is always done in an under-handed way – in fact, most scientists would likely not think their choices are unfair at all. However, I think it is fair to say that many of us are unable to fully account for the ways in which our own a priori conclusions and worldview affect how we make decisions.
The bottom line
Scientific facts are not all there is in an argument. Evidence gets interpreted and valued by scientists differently, and certain assumptions are built into these judgements, all of which an lead different scientists to different conclusions.
What do you think? What did I miss?