6. Verb tenses
You are likely to find yourself shifting between tenses in your paper depending on what aspect of your findings you are discussing. In general, A&A style uses the present tense to describe general facts, findings, truths, methods, and results from papers published within the last ten years. We use the past tense to describe the specific steps of the method used in your study or another study by a different author or group of authors. Here are some tips on when to use the past tense and when to use the present.
6.1 Present simple and past simple
Use the present simple for:
- statements of fact and general truths
- general findings from other authors, particularly recent ones (from the last ten years)
- general methods used in the field (not the specific steps you used in your study)
- general descriptions of your results and findings, including any discussions or conclusions
- descriptions of tables and figures included in the paper
Time markers for the present include: now, usually, often, currently, at present, in this paper, etc. The context will also indicate the tense that is appropriate for each part of your paper. The introduction, for example, tends to offer the reader a general background for the current study so it is typically written in the present tense.
Examples:
- In the usual reduction procedure, the data are measured and flux-calibrated.
- Herschel images allow us to detect new YSOs.
- In this paper, we find that the emission could be fully non-thermal at 5 GHz.
Use the past simple for:
- specific steps you took as part of your method for your study (not general methods)
- specific steps taken as part of a method by other authors and scientists (not general methods)
- specific methods taken by other authors as well as their findings from studies in the distant past (e.g., more than ten years ago)
The past tense is frequently used in the body of the paper where you describe the specific actions you took in your study to achieve your final results, such as: we took, we carried out, we measured, we calibrated, we used, we observed, we calculated, we deduced, we assumed, we concluded.
Examples:
- In our study, we measured and flux-calibrated the data.
- We detected 16 YSOs based on the Herschel images.
- Using this method, we found that the emission was fully non-thermal at 5 GHz.
When describing your findings in the present tense, make sure that you also use the present for recent or current (within the last ten years) findings from other authors. Using the past tense when referring to the work of other authors could suggest that their findings are incorrect or out of date. Their specific methods, however, should remain in the past tense.
6.2 Present perfect and past perfect
These tenses are used to describe actions that occur over an extended period of time or at an unspecified point in time.They are generally not particularly useful in scientific writing.
Examples:
- Astronomers have used many different methods to study the Milky Way.
- The authors had already published their paper by the time we finished ours.
There is also the present perfect continuous tense, which is used to describe an action that began in the past, continues in the present, and may continue into the future. Again, this tense is rarely necessary when writing a scientific paper.
Example:
- The researchers’ results have been useful in providing a background for our own study.
Note: This tense can be used with phrases that serve as indicators of time, such as “in the past few years, in recent years, over the past few years” to extend the action through a period of time.
Example:
- In recent years, several Seifert 2 galaxies have been discovered.
6.3 Present continuous and past continuous
These tenses are not recommended as there is seldom any need for the present or past continuous unless you are describing an ongoing action in the context of a simple action.
Examples:
- We conducted our study as night was falling.
- It was proving difficult to calibrate the instrument due to environmental effects.
6.4 Future
In certain instances, you may use the future tense to describe upcoming studies or new equipment.
Examples:
- Crab pulsar rotation periods will be further examined in a forthcoming paper.
- The JWST will provide greatly improved resolution and sensitivity.
Once in a while, you might find yourself needing to alternate between tenses when discussing things that happened at various points in time.
Example:
- The Hubble deep field consists of 300 images that were taken in 1995. Such a large store of data had never been available before then.